Field of the Invention
The present invention relates to an image forming apparatus using a cartridge.
Description of the Related Art
Electrophotographic image forming apparatuses (hereinafter, referred to as “image forming apparatuses”) perform image recoding in the following manner. An electrophotographic photosensitive member, that is, a photosensitive drum used as an image bearing member is uniformly charged. The charged photosensitive drum is selectively exposed with light, so that an electrostatic latent image (electrostatic image) is formed on the photosensitive drum. Then, the electrostatic latent image formed on the photosensitive drum is developed with toner used as a developer to form a toner image. The toner image formed on the photosensitive drum is transferred onto a recording material such as recording paper or a plastic sheet. Heat and pressure are applied to the toner image which has been transferred onto the recording material to fix the toner image on the recording material.
Generally, such image forming apparatuses require toner supply and maintenance of a process unit. A process cartridge has been in practical use to easily perform the toner supply and the maintenance of the process unit. The process cartridge includes the photosensitive drum, a charging unit, a developing unit, a cleaning unit, and the like which are integrated in a frame. The process cartridge is detachably attached to a main body of an image forming apparatus.
With the process cartridge system, a user can perform the maintenance of the apparatus by themselves. Thus, an image forming apparatus with excellent operability and usability can be provided. Accordingly, the process cartridge system is widely used in the image forming apparatuses.
However, in the image forming apparatus employing such a cartridge system, the cartridge may be erroneously inserted. More specifically, not only a cartridge compatible with the image forming apparatus main body, but also a cartridge incompatible with the image forming apparatus main body might be attached to a cartridge attachment portion in the image forming apparatus main body. The cartridge compatible with the image forming apparatus main body is a cartridge which matches a product model, for example. The cartridges compatible with and incompatible with the image forming apparatus main body are hereinafter respectively referred to as a compatible cartridge and an incompatible cartridge.
One of the methods developed to prevent the erroneous insertion of the incompatible cartridge is discussed in Japanese Patent Application Laid-Open No. 2014-66794. In this method, a boss provided in the incompatible cartridge cannot engage with a movable board disposed adjacent to an opening of the image forming apparatus main body when the incompatible cartridge is inserted to the image forming apparatus main body. More specifically, the above-described configuration includes the movable board having an engaging portion. The movable board engages with the boss of the compatible cartridge while the movable board interferes with the boss of the incompatible cartridge to prevent the further insertion of the incompatible cartridge.